his disease is usually called “White Spot Disease”, since the parasite can be seen with the naked eye as one mm diameter white spots distributed over the body and fins when it is in the trophozoite stage, the feeding phase of the parasite. It should be noted that, despite appearances, the parasites actually sit within the epidermis, and not on the surface. This makes treatment more complicated, as a topical approach will not easily work.
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Deposition of aluminium in gills leads to chloride cell necrosis or at lower levels, to inhibition of the enzymes carbonic anhydrase and/or gill NA+, K+ – ATPase (NKA), required for seawater tolerance. Such changes impair osmoregulatory capacity and cause physiological stress due to disruption of gas and ion transport, altered blood chemistry and hormonal imbalance.
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Saprolegnia often presents as a secondary infection that is diagnosed by the appearance of white or grey cotton-like tufts that, when out of water, have a somewhat mucoid appearance. Typical disease signs are visible circular or crescent-shaped, cotton-wool like, white or grey patches of filamentous mycelia on the fish skin. The lesions appear mainly around the head and the caudal, adipose and anal fins. Lesions may spread over the body until adjacent lesions coalesce.
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We have recently seen a high incidence of cataracts in farmed salmon in several European countries, Canada, and Chile. Salmonids depend on vision for normal feed intake and, not surprisingly, cataracts have been shown to reduce feed conversion efficiency and growth rates, which ultimately raise the cost of rearing fish. Consequently, cataracts can have a significant economic impact on salmonid aquaculture. It is important to note at the outset that “cataracts” is a clinical definition, and their presence does not necessarily mean that changes can...
Infectious salmon anaemia (ISA) is a disease caused by infectious salmon anaemia virus (ISAV), genus Isavirus, family Orthomyxoviridae that affects primarily marine-farmed Atlantic salmon (Salmo salar). Recorded for the first time in 1984 in Norway, it still causes recurrent epidemic outbreaks in Chile. The disease is present in most countries that farm Atlantic salmon: Norway, Scotland, Ireland, Faroe Islands, Canada, USA, and Chile. The virus is adapted to cold-water salmonid fish and has an optimum growth at 15°C. Atlantic salmon is the only species known...
